The present invention relates to a method for the preparation of an L-arabinose solution of a high purity by means of chromatography from a solution containing L-arabinose obtained by hydrolysis of plant tissues.
Plant tissues are mostly composed of cellulose, hemicellulose, lignin and the like and L-arabinose and D-xylose are included in the monosaccharide which constitutes hemicellulose. Although the content of L-arabinose varies depending upon the plant tissues, it has been known that L-arabinose is contained in large quantities in some kinds of plant tissues such as husk of corn grains, ear of stem of corn, bran of wheat and related vegetables, rice bran, squeezed lees of sugar beet and squeezed lees of apple.
Usefulness of L-arabinose in view of its physiological functions has been reported (cf. Japanese Patent Laid-Open Nos. 06/65080 and 07/242551) and the manufacture of L-arabinose by hydrolysis of plant tissues has been investigated (cf. Japanese Patent Laid-Open Nos. 01/312997 and 09/299093). Recently, there has been developed a method for the manufacture of L-arabinose in an industrial scale by hydrolysis of plant tissues containing 10% by weight or more L-arabinose based on dry materials such as husk of corn grains using an acid of as diluted as 0.01-0.5N at 80-150xc2x0 C. (Japanese Patent Application No. 10/137485).
A solution obtained by hydrolysis of plant tissues contains D-xylose in addition to L-arabinose, oligosaccharide such as xylo-oligosaccharide and arabino-xylo-oligosaccharide wherein L-arabinose and/or xylose are/is constituting components (hereinafter, referred to as xe2x80x9coligosaccharidexe2x80x9d) and glucose. Therefore, for an object of effective utilization of L-arabinose, it is desirable to remove such impurities and to prepare L-arabinose of a high purity. The present invention is to meet with such a demand.
In accordance with the present invention, water and a feedstock solution containing at least L-arabinose and oligosaccharide obtained by hydrolysis of plant tissues are supplied to a chromatographic apparatus of a simulated moving-bed system where a solution can be circulated in one direction in an apparatus equipped with a packed bed in which an adsorbent is filled and the solution in the packed bed is moved in one direction whereupon at least L-arabinose and oligosaccharide are separated each other and concentration distribution of each of them is formed in the packed bed. From such a concentration distribution, at least a concentrated L-arabinose solution and a concentrated oligosaccharide solution are extracted from the packed bed and, in addition, a part where their separation is insufficient is made existed at all times whereupon an L-arabinose solution of high purity can be prepared in a high yield.